In a manufacturing process of a semiconductor device, a liquid processing is performed by supplying a chemical liquid such as, for example, a resist, an acid or alkaline cleaning liquid, a solvent, and an insulating film forming precursor-containing liquid, to a substrate from a nozzle. An apparatus for supplying such a chemical liquid is configured to remove foreign substances by interposing a filter unit within a supply passage. For example, Japanese Patent No. 3461725 discloses a resist coating apparatus which is a chemical liquid supply apparatus.
In such a process, bubbles may occur by a gas dissolved within the resist or the chemical liquid. As the line width of a pattern becomes miniaturized, it is required to carefully cope with the fine bubbles that were not problems before.
Japanese Patent Laid-Open Publication No. H04-196517 discloses an apparatus for coating such a processing liquid, in which when a filter unit configured to remove foreign substances within the processing liquid is newly attached (in both cases where the apparatus is started up or the filter unit is replaced), a process of removing a gas within the filter unit by flowing the processing liquid into the attached filter unit is performed (hereinafter, referred to as “filter wetting”). In a conventional filter wetting method, filtration is performed by a positive pressure (e.g., a pressure not lower than an atmospheric pressure) caused by N2 gas or a pump after setting of a filter unit, and the number of defects caused by bubbles is monitored on a wafer. Then, at a point of time when the number of defects is decreased to a predetermine level, the gas within the filter unit is considered to be removed, and the process is considered to be completed.
However, from the viewpoint of a mass production cost, it is required to reduce a processing liquid to be consumed until the start-up of the filter unit, and to shorten a start-up time.